摘要:

To clarify the spatial localization of dopamine (DA) and norepinephrine (NE) in the basal hypothalamus of the rat, superficial, intermediate or deep portions of the basal hypothalamus were assayed for these amines. Superficial basal hypothalamic specimens (av. wt. 0.45 mg) comprising mainly the median eminence (ME) had the highest concentrations of DA (>10 µg/g tissue). The intermediate and deep specimens, which included increasing amounts of tissue adjacent to and deep to the ME, had lower concentrations (5 and 3 µg/g, respectively). In contrast, the concentrations of NE did not differ in the three preparations and averaged 2 µg/g. The concentration of epinephrine, a substance which can interfere with the assay for NE, was less than 0.1 µg/g. These results indicate that DA in the basal hypothalamus is concentrated in the ME, and confirm previously published histochemical and pharmacological studies indicating that DA is the predominant catecholamine in this reg

ISSN:0028-3835    

DOI:10.1159/000122205

出版商:S. Karger AG    

年代:1973

数据来源: Karger

摘要:

Plasma prolactin levels were measured by radioimmuno-assay in free-moving lactating rats bearing heart cannulas. Litters adjusted to 6 pups were returned to the mothers after a separation of 8–12 h from days 6 to 15 postpartum. Blood samples were taken before and 15, 30, 60 and 120 min after suckling had resumed. Lactating mothers were treated at various intervals before the experiment with P-chlorophenylalanine (PCPA), an inhibitor of serotonin (5-HT) synthesis; some animals were treated in addition with 5-hydroxytryptophan (5-HTP), a direct precursor of 5-HT. Blockade of 5-HT biosynthesis completely inhibited the more than 10-fold increase in prolactin levels observed in untreated controls. Inhibition of the prolactin response lasted more than 48 h after administration of PCPA; complete recovery required 120 h. Treatment with 5-HTP, which antagonizes the depletion of 5-HT caused by PCPA, restored the ability of the animals to release prolactin in response to suckling. The basal prolactin levels observed in lactating animals deprived of pups were not significantly affected by either drug at the time of experimentation. The results are consistent with the hypothesis that serotonin-containing neurons have a facilitatory effect on the hypothalamic mechanisms which trigger prolactin release in response to neural inputs involved in the suckling stimulu

ISSN:0028-3835    

DOI:10.1159/000122206

出版商:S. Karger AG    

年代:1973

数据来源: Karger

摘要:

ACTH release in stress, measured by changesin the plasma corticosterone level, was studied in rats 24 h after isolation of the pituitary by surgical ablation of the medial hypothalamus. Injection of E. coli endotoxin or a large dose of formaldehyde induced a significant increase in ACTH release, whereas either sham-adrenalectomy under ether anesthesia or a small dose of formaldehyde did not. Resting as well as stress-induced increases in ACTH release were depressed by dexamethasone pretreatment after the removal of medial hypothalamus. It was concluded that some of the pathways through which E. coli endotoxin and a large dose of formaldehyde release corticotrophin may bypass the medial hypothalamus; and, further, that the feedback action of dexamethasone may exert itself outside the hypothalamus.

ISSN:0028-3835    

DOI:10.1159/000122207

出版商:S. Karger AG    

年代:1973

数据来源: Karger

摘要:

Normal, intact rats generally show transient elevations of pituitary-adrenal hormones in response to acute stress. The immediate hypersecretion, followed by return to baseline levels after approximately 2 h, is believed to be due to CRF of median eminence origin (ME-CRF). Lesioned rats, on the other hand, do not usually exhibit an immediate response, but under certain conditions show a delayed hypersecretion of pituitary-adrenal hormones 2–4 h later. From our previous studies it has been demonstrated that the delayed response of lesioned rats is due to release of tissue-CRF. To examine the relationship between ME-CRF and tissue-CRF, groups of lesioned animals were subjected to the stress of plasma injection or laparotomy. Both stimuli produced a delayed hypersecretion of corticosterone 2–8 h later. When, however, ME-CRF or ACTH was administered at the time of application of the stress, the expected delayed response was significantly suppressed and plasma corticosterone levels approached baseline values. To determine how the delayed response was suppressed, one group of lesioned-hypophysectomized donor rats was subjected to laparotomy stress and 5 h later the blood from these animals was assayed for tissue-CRF. Another group of lesioned-hypophysectomized rats was not only subjected to the laparotomy stress but also injected with ACTH at the same time and then tested for blood CRF activity 5 h later. Prior administration of ACTH caused a significant reduction in the tissue-CRF levels in the peripheral blood. Therefore it appears that suppression of the delayed response by ME ext

ISSN:0028-3835    

DOI:10.1159/000122208

出版商:S. Karger AG    

年代:1973

数据来源: Karger

摘要:

The effect of complete transection or hemisection at various levels from the lumbar through the cervical spinal cord on a stress-induced change in plasma corticosterone concentration was studied in adult male pentobarbital-anesthetized rats. Stressors were a hind-leg tourniquet 1–5 days and a hind-leg break 5 or 10 days postoperatively. A rise in plasma corticosterone concentration 20 min after the onset of the stress was generally used as an index of ACTH secretion. Neither stressor stimulated ACTH secretion in rats with complete cord transection between L1 and T2. Hemisection between L1 and T10 did not consistently block ACTH secretion following ipsilateral or contralateral tourniquet or leg break, but hemisection above T10 blocked the effect of only the contralateral stressors. Complete cord transection above T2 was associated with elevated ‘basal’ plasma immunoreactive ACTH and corticosterone concentrations in unanesthetized rats. These elevations were partially suppressed by pre-treatment with dexamethasone 12 h prior to sacrifice. We conclude that both tourniquet and leg break stimulate ACTH secretion through pathways in the spinal cord. These pathways are not consistently lateralized between L1 and T10 but are contralateral to the stimulated extremity above T10<

ISSN:0028-3835    

DOI:10.1159/000122209

出版商:S. Karger AG    

年代:1973

数据来源: Karger

摘要:

Enucleated and enucleated+Harderianectomized (E+H) 12-day-old rats were exposed to an additional 5 h of light or placed in the dark at 17.00. Body temperatures were lower in both groups in the dark in comparison to rats with comparable treatments in the light. These results suggest that removal of the Harderian gland does not alter the animal’s response to environmental temperature. Intact, suckling animals were placed in the dark at 7, 22, and 34°C for 4 h or left with their mother. Pineal N-acetyltransferase was significantly higher in the group at 22 °C than in any other group, suggesting that the activity of this enzyme is influenced by environmental temperature in suckling rats. Pineal serotonin (5-HT) shows little change under these conditions. However, if rats at these temperatures also are exposed to overhead lighting, dramatic increases occur in pineal 5-HT at both 22 and 34 °C. N-acetyltransferase levels are significantly lowered at 34°C only; pineal HIOMT does not change. These findings are compatible with the hypothesis that light and temperature both regulate pineal function in the suckling rat, probably by different mechanisms. The diurnal variation in pineal 5-HT in 12-day-old E+H rats is abolished by constant light for 3 days but not by constant dark. This pattern is similar to that found in intact adults in constant light or constant

ISSN:0028-3835    

DOI:10.1159/000122210

出版商:S. Karger AG    

年代:1973

数据来源: Karger

摘要:

Limbic modulatory influences on hypothalamic adrenocorticotropic activity were investigated by means of electrical stimulation through chronically implanted deep electrodes in the conscious unrestrained pigeon, and by means of bilateral electrolytic lesions. Hippocampal stimulations or lesions were found to induce either a marked drop or rise in plasma corticosterone concentration. Archistriate stimulation ted to an increase of corticosterone (B) titer. Diurnal variations in corticoid level were suppressed after lesion placement in the hippocampus, but stress-induced responses were only slightly reduced. No behavioral signs were detected during and after periods of stimulation.

ISSN:0028-3835    

DOI:10.1159/000122211

出版商:S. Karger AG    

年代:1973

数据来源: Karger

摘要:

The pituitary glands of mature male rats were removed and either exposed to ice cold buffer solution or kept at room temperature for 5–15 min, and then incubated at 37°C. The levels of GH, LH and prolactin, released into the medium, were measured by specific radioimmunoassays. The pre-cooling of the pituitary glands augmented the basal release of these pituitary hormones during the first 1-hour period of incubation. Purified pig hypothalamic fractions were tested for GH-releasing hormone (GH-RH) and prolactin release-inhibiting factor (PIF) activity under the cooling or non-cooling conditions. PIF activity was demonstrated only when pituitaries were not exposed to cooling. GH-RH activity was not demonstrated under either condition in the fraction containing P

ISSN:0028-3835    

DOI:10.1159/000122212

出版商:S. Karger AG    

年代:1973

数据来源: Karger

摘要:

Electron microscope studies revealedthat 6-hydroxydopamine (6-HODA) destroyed the aminergic (type ‘B’) neurosecretory axons entering the rostral pars distalis of the teleost Tilapia mossambica. 6-HODA had no effect upon plasma sodium or pituitary prolactin levels in seawater (SW) fish, although it prevented the fall in plasma sodium levels normally associated with transfer to fresh water (FW). Furthermore, the prolactin cells of 6-HODA-treated fish transferred to FW were activated as judged by ultrastructural and physiological criteria. These observations lead us to suggest that neurosecretory axons of hypothalamic origin and plasma osmolality interact to regulate teleost prolactin cells. On the other hand, 6-HODA evoked no obvious ultrastructural changes in the ACTH cells and no significant alterations in plasma cortisol concentrations. Thus, it would appear that type ‘B’ axons do not provide the major control of ACTH secretion in Tila

ISSN:0028-3835    

DOI:10.1159/000122213

出版商:S. Karger AG    

年代:1973

数据来源: Karger

摘要:

Receptive fields and response thresholds were determined by stimulation with a camel hair brush and von Frey hairs during recording from a specific branch of the pudendal nerve, in untreated and estrogen-treated ovariectomized female rats. The receptive field of this pudendal nerve branch is located on the perineal skin of the female rat, extending in some cases onto the back of the leg. Estrogen treatment caused an expansion of the receptive field, and a trend toward increased receptor sensitivity within the receptive field. The estrogen effect is appropriate to the type of stimulation applied by the male rat during induction of the lordosis response: pelvic thrusting by the male contacts the area of the female’s skin included in this receptive field and should result in phasic responses, which we find to be estrogen-sensitive, rather than tonic, long-sustained responses, which are not estrogen-sensitive. In these pudendal nerve recordings, there were considerable overlaps between estrogen-treated and untreated groups both in receptive field size and sensitivity. Unless specific, strongly estrogen-sensitive receptors have been partially masked by our stimulation and recording methods, it does not seem likely that this peripheral, somatosensory estrogen effect could by itself account for the overall estrogen effect upon the lordosis refle

ISSN:0028-3835    

DOI:10.1159/000122214

出版商:S. Karger AG    

年代:1973

数据来源: Karger